This invention relates to the removal of soil from fabric, and, more particularly, to a process for improving the dislodging of soil from the fabric and preventing its redeposition onto the fabric.
Garment dry cleaning is currently performed commercially using organic solvents such as perchloroethylene or petroleum derivatives. These solvents pose a health hazard, are smog-producing, and/or are flammable. The use of dense-phase carbon dioxide (both liquid and supercritical) as a dry-cleaning solvent medium resolves the health and environmental concerns posed by conventional solvents. An additional benefit is that its use reduces secondary waste streams associated with processes that employ conventional solvents. A dry-cleaning process that uses liquid carbon dioxide as a cleaning medium is described in U.S. Pat. No. 5,467,492. In one embodiment, the fabric is placed into a perforated basket within a pressure vessel, and then submerged into a pool of liquid carbon dioxide. The liquid carbon dioxide and the fabric in the pool are agitated by an incoming flow of liquid carbon dioxide that induces a tumbling action of the fabric. The liquid carbon dioxide solvent promotes the removal of the soluble soils through their dissolution, and the mechanical action of the fabric tumbling promotes the expulsion of the soil.
One of the disadvantages of this liquid carbon dioxide process is that it must be performed within a pressure system, and thus has associated high capital costs. An apparatus and method are described in U.S. Pat. No. 5,651,276 to expel soils from fabrics by gas jets at ambient pressure. This gas jet process may be practiced using the apparatus of the liquid carbon dioxide process described above, as a step of an overall fabric dry-cleaning process, or in a separate, low-cost apparatus.
In this process, the dislodged soil is desirably entrained in the gas and thereafter removed in a mechanical filter. The gas jet process promotes the dislodging of the soil from the fabric, the entraining of the soil in the gas flow, and the collecting of the soil using a filter before it is redeposited back onto the fabric. Although existing gas jet techniques achieve these objectives to some extent, it is always desirable to improve the efficiency of the gas jet process even further.
There is a need for an approach that realizes the advantages of the gas jet process, while increasing the effectiveness of the dislodging of the soil from the fabric and reducing its redeposition back onto the fabric prior to removal of the soil from the gas flow by filtration. The present invention fulfills this need, and further provides related advantages.